1. Field of the Invention
The present invention relates to the field of formation fluid sampling and analysis and in particular to the field of reservoir characterization using photoacoustic spectroscopy.
2. Summary of the Related Art
To obtain hydrocarbons such as oil and gas, boreholes are drilled into the earth by rotating a drill bit attached to the end of a drill string. Modern directional drilling systems generally employ a drill string having a bottom hole assembly (BHA) and a drill bit at an end thereof that is rotated by a drill motor (mud motor) and/or by rotating the drill string. A number of downhole devices placed in close proximity to the drill bit measure certain downhole operating parameters associated with the drill string. Such devices typically include sensors for measuring downhole temperature and pressure, azimuth and inclination measuring devices and a resistivity-measuring device to determine the presence of hydrocarbons and water. Additional downhole instruments, known as logging-while-drilling (LWD) tools, are frequently attached to the drill string to determine the formation geology and formation fluid characteristics and conditions during the drilling operations. Analytical sampling devices are also deployed from the wireline into a wellbore after drilling.
Commercial development of hydrocarbon fields requires significant amounts of capital. Before field development begins, operators desire to have as much data as possible regarding the nature of the hydrocarbon formation, in order to evaluate the reservoir for commercial viability. Despite the advances in data acquisition during drilling using the MWD systems and wire line analysis applications, it is often necessary to conduct further testing of the hydrocarbon reservoirs in order to obtain additional data. Therefore, after the well has been drilled, the hydrocarbon zones are often tested with other test equipment such as wire line tools, which are used to further analyze and monitor the formation. Samples are taken from different wells at different locations in the reservoir. These samples are compared to estimate reservoir compartmentalization of the reservoir.
The degree of reservoir compartmentalization is of great commercial importance. Multi-billion dollar decisions on how to develop a reservoir (well location, types of production facilities, etc.) are based on whether or not a reservoir is compartmentalized. Oil producers want to know whether different sections of a reservoir are separate compartments (across which fluids do not flow) or whether they are connected. Separate compartments must be drained separately and may need different types of processing for their fluids. Thus, there is a need for an accurate method and apparatus for determining whether or not a reservoir is compartmentalized.